The professor sighed. It was a real, sad sigh. Maybe he realized for the first time he was just speaking to three guys in overalls in a barroom. Or maybe he didn’t care.

He said, “You don’t find many fossils. Think how many animals lived on Earth altogether. Think how many billions and trillions. And then think how few fossils we find. – And these lizards were intelligent. Remember that. They’re not going to get caught in snow drifts or mud, or fall into lava, except by big accident. Think how few fossil men there are – even of these subintelligent apemen of a million years ago.”

He looked at his half-full glass and turned it round and round.

He said, “What would fossils show anyway? Metal belts rust away and leave nothing. Those little lizards were warm-blooded. I know that, but you couldn’t prove it from petrified bones. What the devil? A million years from now could you tell what New York looks like from a human skeleton? Could you tell a human from a gorilla by the bones and figure out which one built an atomic bomb and which one ate bananas in a zoo?”

“Hey,” said Joe, plenty objecting, “any simple bum can tell a gorilla skeleton from a man’s. A man’s got a larger brain. Any fool can tell which one was intelligent.”

“Really?” The professor laughed to himself, as if all this was so simple and obvious, it was just a crying shame to waste time on it. “You judge everything from the type of brain human beings have managed to develop. Evolution has different ways of doing things. Birds fly one way; bats Ay another way. Life has plenty of tricks for everything. – How much of your brain do you think you use. About a fifth. That’s what the psychologists say. As far as they know, as far as anybody knows, eighty per cent of your brain has no use at all. Everybody just works on way-low gear, except maybe a few in history. Leonardo da Vinci, for instance. Archimedes, Aristotle, Gauss, Galois, Einstein -”